Interesting. We have recently heard a call for all countries in the EU to have equal wages seeing they have the same currency. England backs away from this. Now we have a shot at instant welfare for migrants, who may travel to the UK any time they want. This would load the UK (not the EU as a whole) with a welfare burden. The UK of course will resist this.
There is a game of chess going on here. One side is maneuvering for UK to be subsumed into EU, the other fighting for UK's sovereignty.
I believe the UK will stay essentially separate. The major reason is that the 'CITY OF LONDON' will want to gain command over Europe as big big resource block.